Nowadays processes and devices are known to separate mixtures of different materials originating from shredder fractions and to treat them for re-usage possibility. For doing so ferrous-magnetic metal particles are separated from non-magnetic particles, plastics from nonferrous heavy metal on the one-hand side, and on the other hand, inflammable material from flammable materials. There are problems with such a separation for plastic materials, since today law requests an exact separation of such materials, in order to recycle each individual plastic component in a material specific way. Sifters, operating in accordance with material density ratio, and which are used in generally well-known processes for separating plastics, use air as flotation fluid. The results achieved by this type of sifters are unsatisfactory. At the end of such processes a mixture of different plastic components is received that is still not pure with regard to individual plastic components. One reason is essential for such unsatisfactory results. That is, density of different kind of plastics varies so little from one another that such a procedure must lead to unsatisfactory results. Settling of plastic material in an air stream results in no clear separation of different kind of plastic materials. Such processes result in a conglomerate of different types of plastics that settle on the bottom of a flotation tank.
There are known further processes and devices to separate different kinds of material, e.g. light and heavier fibers, colors and so on, for which liquid is used as flotation medium and in which lighter particles of the material to be separated were kept in a floating zone in poise by aerating the flotation medium. Such lighter material is transported to the surface of the flotation medium and can there be skimmed. Heavier particles of the material to be separated sink, due to gravity, to the bottom of the flotation tank and are skimmed in the bottom area (see AT 411,155 B and DE 197 33 059 C2). These processes and devices are not suitable for separation of plastics, since plastic materials easily re-float to the surface due to their only slight differences in density and relatively big surfaces of individual particles. Hence, it is essential that re-floating of already settled particles be prevented. An embodiment similar to this invention is not deducible from that state of the art and is perhaps even not wanted for the materials to be separated by the state of the art. Lost separating liquid will be added.
A precise separation of plastic materials in correspondence with their individual chemical composition is not or hardly possible with the aforementioned processes and devices. Hence, it is excluded to re-use plastics that are obtained by one of these processes or devices, in correspondence to their inherent characteristic features.
According to the state of the art they will enter into thermal utilization since such utilization does not require a clear separation of plastics with regard to their chemical composition.
It is one task of this invention to create a process and a device that leads to a clear separation of plastic materials in accordance with their chemical composition.